The overall adaptability, functionality and viability of an internal combustion engine is dependent upon the ability to precisely provide the correct air/fuel (“A/F”) ratio that is best suited for the varying operating conditions of the engine. The current state of the art of engine fuel management comprises various forms of computer controlled electronic fuel injection systems. While the use of fuel injection systems generally results in improved engine performance as a result of better A/F mixing and control (such as compared to carbureted engines), the development of computer controlled fuel injection and its almost universal use was driven by the need to comply with the increasingly more stringent exhaust emissions regulations. In particular, such computer controlled engine management systems are designed to constantly monitor and adapt to changing conditions to maintain emissions compliance.
The most common engine control systems are closed loop systems that continuously alter the amount of fuel delivered to the engine based on the output of sensors that directly monitor engine exhaust. In such systems, a specific sensor output value is selected that complies with emissions, and then the quantity of fuel which is delivered to the engine is increased or decreased in an effort to maintain engine exhaust with a sensed output near the selected value. In such a configuration, the engine is controlled so that it operates in a manner which complies with emissions requirements, and not necessarily in a manner which maximizes engine performance (such as engine power output).
Current emission regulations focus on normal vehicle street operations within legal speed limits and under conditions of low to moderate acceleration. This is because the engine A/F ratios that correspond to engine exhaust levels which meet emissions requirements are generally not those A/F ratios which are required to operate the engine in a high power output range or “Power Mode.” An engine may be run in Power Mode, for example, when a vehicle is passing, climbing hills, towing or under other situations of heavy acceleration or heavy load. Because of this, engines are generally required to meet emissions requirements under normal operating requirements and not in Power Mode. As such, the engine control systems of most vehicles only utilize a closed loop fuel control mode during normal engine operating mode and not during operation of the engine in Power Mode. During Power Mode operation, the A/F ratios are controlled by a preprogrammed set of fuel maps and mathematical formulas and fuel delivery is not controlled to maintain specified emissions levels as monitored by the sensors, but rather is controlled in an “open loop”. Commonly this manner of engine control is referred to as closed-loop during the emissions mode and open-loop during Power Mode.
In such a configuration, engine performance can be enhanced during operation in Power Mode because the engine's operation is not controlled so as to meet emission regulations. On the other hand, the engine's performance is still not optimized because during Power Mode the A/F ratio is determined from the fuel maps. The operation of a particular engine at a particular time may not closely match the conditions which were used to generate the fuel tables. In this regard, the open-loop operation of the engine during Power Mode does not ensure that the engine control is varied based upon operating conditions to maximize engine performance.
The automotive and motorsports aftermarket industry provides consumers with a large variety intake, exhaust or other engine modification products for the purpose of increasing engine performance. A problem with these modification products is that optimal gains can often only be realized with associated modifications to the OEM fuel delivery system. In particular, when a consumer makes an engine modification, such as a modification to the intake or exhaust system that goes beyond the OEM fuel system parameters, performance and functionality of the engine can suffer if associated changes are not made to the engine control system. As a result, in order to obtain maximum gains, consumers may be forced to modify either specific sensor outputs (thus affecting a bias to the stock fuel map or devices that directly modify the stock fuel pulse width), replace the OEM engine controller or entirely re-program the controller so that it works with the modified engine.
In one arrangement, a consumer may attempt to increase engine performance by modifying the engine so that it operates in a closed-loop condition during Power Mode, rather than being controlled in an open-mode based upon fuel tables and with no regard to actual engine conditions. For example, a consumer may install modified or additional sensors, such a wide band oxygen sensor or an air mass sensor or both, so that the engine may be operated continuously in a closed-loop arrangement (including during Power Mode). The output of these sensors may be utilized to provide additional or modified control signals by the OEM engine controller. These modified signals may be used to target both operation of the engine in emissions mode operation and in Power Mode operation.
However, such a modification has various drawbacks. Among them is that the consumer must install and use of one more secondary sensors. These sensors can themselves be expensive and they can be expensive to install and maintain. In addition, such a modified control arrangement still controls fuel delivery based upon feedback from sensors which measure secondary engine variables such as air flow or exhaust, rather than direct reference to actual engine power or performance.